1. Technical Field
The present disclosure relates in general to wireless communication devices and in particular to radio frequency (RF) tuning in wireless communication devices.
2. Description of the Related Art
Traditional voltage-tunable tuning circuit components such as Barium Strontium Titanate (BST) components operate utilizing a bias voltage which can be as high as 20V or more. Long-term operation of these tuning circuit components at higher voltages, combined with higher temperatures, can degrade tuner component reliability. In some cases, BST component reliability can be impaired especially for heavy communication usage of corresponding wireless communication devices, such as smart-phones. This heavy usage results from device users who actively use RF data and voice communication services for several hours a day, especially at elevated temperatures. The reliability impairments at higher temperatures and operating voltages are not unique to BSTs. Most semiconductors and other related components experience some level of degradation. However, the degree of such degradation is material-specific.
Micro-electro-mechanical systems (MEMs) tuners also face component reliability challenges. MEMs tuners employ an array of small capacitor elements. Each element is usually in the form of an arm or beam shape that can be moved to bring the two plates of a capacitor closer together or farther apart. Many elements are electrically combined to form a variable capacitor. The capacitance of the overall device is varied by controlling the number of elements that are in the low or high capacitance state.
For MEMs tuners, one of the primary types of failure is mechanical failure of the materials or structures of individual tuning circuit components. The cause of this mechanical failure is associated with the number of actuation cycles (changing position from low to high capacitance or high to low capacitance) occurring within a tuning circuit component. For mobile devices which are typically always powered on to receive service, billions of actuations over the life of a MEMS tuner are likely to occur. A tuner providing a receive antenna match can accumulate as many as 1 billion cycles per year under normal daily device use. This normal daily use includes an idle mode operation, in which the device is powered on and periodically monitors a wireless paging channel and measures neighbor cell power, as well as a connected (or “active”) mode, where the user is in an active data or voice session. In the worst case, the state of some tuning circuit components may change for a majority of those paging and measurement events while other tuning circuit components rarely change state.